Don't short the track pickups to the motor connections:

The #1 thing that people do wrong is not isolate the track pickups from the motor. You NEED to get an inexpensive meter, set it to test continuity/resistance/ohms. Make sure that before installation that of these 4 connections:

Motor plus

Motor minus

track pickup right rail

track pickup left rail

NONE of these can connecto to the other, although notice that the motor plus and minus will have a low resistance through the motor, not zero ohms

Also, if you are battery, make sure nothing connects to the wheels, the track/battery switch on Aristo locos are NOT to be trusted.

You can permanently damage the decoder if you short the motor connections to the track connections on the decoder, and it's easy for the manufacturer to tell you did this.

Don't physically damage the decoder:

On the Revolution, be careful of the small sockets, and get the RIGHT connector. If you got one of these used, chances the previous owner lost one of the plugs if he did not use it. They can be bought as replacements, but notice they are all different sizes. The chuff one is particularly small and harder to find.

On the Titan, the screw terminals are a bit forgiving, but you CAN destroy them. Use a light touch, and open all of them before installation, counter clockwise. Look at them carefully and notice that if they are open, there are shiny bits above AND below the hole where the wire goes. When they are closed without a wire, it may look like they are open, but the shiny bits are all at the top of the hole. Just open and close one and look with a magnifying glass if this is not clear. If you break one, then you won't have a reliable connection at this point.

Existing lights

Never assume the power for the lights is correctly hooked up in any model! Trace the wires, look where the common goes. Note many Aristo locos, while they have the "socket" have several lights connected directly to the track pickups, and often the headlight and rear headlight are wired to a regulator, which then goes to the socket. It's often best to pull out the bulbs, and wire LEDs directly to the decoder.

Fan

DO NOT connect the fan to the track, but connect it to either the "18v" output or better yet the 5v output. Connecting to the track can interfere with programming.

Using Titan without a socket:

Many people are eager to cut the pins off a Titan, saying, I'm hard wiring this, only to later want to put it into a loco with a socket. I make little blocks of cheap perf board as sort of a socket with no connections: